1. Technical Field
The present disclosure generally relates to optical plates and, more particularly, to an optical plate employed in a backlight module.
2. Discussion of the Related Art
Referring to FIGS. 10 and 11, a typical direct type backlight module 100 includes a housing 11, a plurality of light sources 12, a light diffusion plate 13, and a prism sheet 10. The light sources 12 are positioned in an inner side of the housing 11. The light diffusion plate 13 and the prism sheet 10 are positioned on the light sources 12 above a top of the housing 11. The light diffusion plate 13 includes a plurality of diffusing particles (not shown) to diffuse light. The prism sheet 10 includes a transparent substrate 101 and a prism layer 103 formed on a surface of the transparent substrate 101. A plurality of elongated V-shaped ridges 105 are formed on the prism layer 103.
Light emitted from the light sources 12 enters the diffusion plate 13 and becomes scattered. The scattered light leaves the diffusion plate 13, travels through the prism sheet 10, and is refracted out at the elongated V-shaped ridges 105.
The refracted light leaving the prism sheet 10 is concentrated at the prism layer 103 and increases the brightness of the prism sheet 10. The refracted light propagates into a liquid crystal display panel (not shown) positioned above the prism sheet 10.
However, although the light from the light sources 12 enters the diffusion plate 13 and becomes scattered, many strong light spots are still formed.
To reduce or eliminate the strong light spots, the backlight module 100 may include an upper light diffusion film 14 positioned on the prism sheet 10.
However, a plurality of air pockets exist around the boundaries of the light diffusion film 14 and the prism sheet 10. When the light passes through the air pockets, some of the light undergoes total reflection along one or more boundaries. In addition, the upper light diffusion film 14 may absorb some of the light from the prism sheet 10. As a result, light illumination brightness of the backlight module 100 is reduced.
Therefore, a new optical plate is desired to overcome the above-described shortcomings.